1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method and a program, and particularly relates to an image processing apparatus, an image processing method and a program capable of providing 3D images with less sense of discomfort and uncomfortable feeling for human beings by adjusting parameters of monocular 3D information based on visual sense characteristics of human beings.
2. Description of the Related Art
As a method of displaying a 2D image on a 2D display and allowing a viewer to perceive the 2D image as a 3D image, there exists a method of presenting a 2D image for a left eye and a 2D image for a right eye in which binocular parallax (parallax between the left eye and the right eye) to the left and right eyes of the viewer respectively.
As information for allowing a human to perceive stereoscopic effect and depth of an object, there are binocular 3D information by both eyes and monocular 3D information by a single eye. A human perceives stereoscopic effect and depth of the object or space by combining the monocular 3D information and the binocular 3D information. As the binocular 3D information, for example, binocular parallax, horizontal convergence and the like can be cited. As the monocular 3D information, for example, shading, contrast, color, a spatial frequency, shielding relation and the like can be cited.
When stereoscopic effect and depth are desired to be enhanced in the case of displaying the 2D image on the 2D display and allowing the viewer to perceive the 2D image as the 3D image, for example, a method of increasing binocular parallax which is one of the binocular 3D information can be considered.
However, to increase the binocular parallax has the following problems in the light of an ocular structure and visual sense characteristics of human beings. That is, human eyeballs are normally in a parallel or a rather inward convergence state, therefore, when the binocular parallax is increased more than the distance between pupils, the eyeballs are in a divergence state in which both eyes are directed to the outside. The distance between pupils differs depending on the age or sex, therefore, a person having distance between pupils which is smaller than the normal distance is liable to be in the divergence state.
In the real world, sight lines of both eyes are directed to a gaze point as well as the focus of eyes is achieved on the point, therefore, distance of convergence of eyeballs corresponds to distance of adjustment thereof. However, when allowing the viewer to perceive the 3D image by the 2D image for the left eye and the 2D image for the right eye, the convergence can be adjusted on a position perceived as the 3D image, while the adjustment is focused on an image display surface, therefore, the distance by convergence of eyeballs does not corresponds to the distance by adjustment thereof. Accordingly, to emphasis stereoscopic effect and depth by increasing binocular parallax changes the distance by the convergence of eyeballs and the distance by the adjustment to a direction not correspond to each other, which may allow the viewer to perceive artificiality or to feel discomfort and visual fatigue.
In order to reduce uncomfortable feeling and visual fatigue, a method of adjusting the binocular parallax is proposed. For example, in a method proposed in Japanese Patent No. 3749227 (Patent Document 1), plural sample images in which binocular parallax is set to different values are presented and whether the presented images are permitted or not is allowed to be responded to adjust the binocular parallax.
However, when uncomfortable feeling and visual fatigue of the viewer are intended to be reduced, the binocular parallax is basically adjusted to a direction of reducing the stereoscopic effect and depth, therefore, realistic sensation and reality are reduced. Additionally, when stereoscopic effect and depth perceived by binocular 3D information are different from stereoscopic effect and depth perceived from monocular 3D information, the viewer may feel artificiality.
Therefore, it is not preferable that stereoscopic effect and depth sense of the 3D image are enhanced by increasing the binocular parallax.
On the other hand, a method of enhancing stereoscopic effect and depth sense by using monocular 3D information is also proposed. For example, in JP-A-2001-238231 (Patent Document 2), a method of changing characteristics of shading, shielding relation and a blurring state according to a depth position of an object in an image to enhance the depth sense is proposed.